Piston-casting.



Y J. H. BAMBERG. f P'IiSTON CASTI-NG. APPLICATION FILED MAR. 6, 1917 1,296,592. I PatentedMar. 4, 1919.. I

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WITNESS.- v INVENTOR.

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- A TTORNEY.

I. H. BAMBERG.

PISTON CASTING. APPLICATION FILED MARI'G. |9|1.

1,296,592. T Patented Mar.'4,1919.

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WITNESS: INVENTOR.

' ATTORNEY.

bustion motor, and which will require a.

UNITED STATES" PATENT OFFICE.

JOSEPH H. BAMBERG, 0F TOLEDO, OHIO, ASSIGrN'OR TO THE ALUMINUM CASTINGS COMPANY, OF QLEVELAND, OHIO, A CORPORATION OF OHIO. I

PISTON-CASTING.

Specification of Letters Patent.

Patented Mar. 4', 1919.

Original application filed March 7, 1916, Serial No. 82,529. Divided and this application filed March 6,

1917. Serial No. 152,896.

To all whom it ma 3 concern:

Be it known that I, JOSEPH H. BAMBERG, a citizen of the United States, residin at T0- ledo, in the county of Lucas and btate of of relatively low specific gravity and which is relatively non-porous, free from entrapped air and other gases and oxids and other foreign materials.

Another object of my invention is to provide a skirted'piston cast of metal or me tallic alloy of relatively low specific gravity and readily machinable to provide durable and efiicient bearing surfaces.

Another object of myinvention is to provide a casting for a skirted piston for an internal combustion motor made from metal or metallic alloy of relatively low specific gravity and having different structural characteristics at various sections. as desired.

Another object of my invention is to provide a skirted piston casting of metallic alloy having a relatively low specific gravity and a relatively high coeflieient of heat conductivity, which when machined and used in the cylinder of an internal combustion motor will not collect carbon to the same extent as does an iron piston and will take and retain a relatively high polish because of its fine-grained structure.

Another object of this invention is to provide a skirted piston casting made of a nun-imam volume of metallic alloy of relatively lo'- specific gravity and high heat conductivity, which will not disintegrate nor undergo changes in its internal structure under ordinary usage in an internal comminimum amount of machining.

Another object of my inventionis to provide a skirted-piston casting made of a metallic alloy of relatively low specific gravity and high heat conductivity and in which casting there is a relatively small amount of vide a piston casting of an alloy containing aluminum, tin and copper, having a structure relatively fine-grained, non-porous and free from entrapped air and other gases and from oxids and other foreign materials.

Other objects of my invention will be obvious to one skilled in the art from the description of it hereinafter made.

The present application is a division of my pending application, Serial No. 82,529, filed March 7, 1916, in which I have fully set forth and explained an apparatus and method suitable for the production of the piston casting to which the present application relates.

In order that the present invention may be clearly understood, I have shown in the accompanying drawings one form of piston casting embodying my improvements and also a mold in which the casting is formed.

Figure 1 is a perspective view of a skirted or cup-shaped piston casting, after the sprue has been removed.

Fig. 2 is a. central longitudinal sectional View through the piston casting.

Fig. 3 is a central longitudinal sectional view of the piston casting taken at right angles to the section shown in Fig. 2.

Fig. 4 is a bottom plan view of the piston casting.

Fig. 5 is a side elevation of a mold adaptedfor the production of my improved p-ls attached to one of them. I

The piston casting, as to outward formation has the usual piston head and side wall 2 characteristic of the skirted pistons commonly employed in internal combustion engines. The side wall is formed with diametrically opposite inwardly projecting bosses 3, 3 which" are cored out to receive a wrist-pin. The upper part of the casting, as shown, is provided with strengthening and heat-dissipating ribs 4 and 5.

improvements are not limited to the particular conformation of the casting shown but may be varied widely, as will be understood from the following explanation of the matters which characterize my improvements.

The physical properties and internal structural characteristics which chiefly characterize my invention are the result of the constituent materials employed in the casting and the manner in which the casting is formed. "1 .will, accordingly, briefly describe a mold designed for the production of the casting and the manner in which such mold is used. For a full description and expladucing the casting by means of it, reference is had to my pending application, Serial No.

82,529, above referred to.

Referring to Figs. 5 and 6, the mold comprises a base member a and complementary members 6 and c, movable on the base member (1 toward and from each other. (Z indicates as an entirety the main core part of the mold. This core is formed in a plurality of sections which are suitably recessed to form the bosses 3, 3 and ribs 4 and 5 on the interior of the piston. e, e are diametrically opposite core pins arranged to project into the mold cavity to form openings in or through the bosses 3, 3 of the piston casting. These core pins are in the form of rods which are slidably mounted in alining openings of the mold'members b and 0..

Themold members I) and 0 are formed with complementary cavities or recesses I) and c which together form the mold gate.

The gate thus formed, as will be observedfrom Fig. 6, is disposed midway between the internal bosses 3, 3 of the piston casting. As is fully explained in my co-pending application referred to, I prefer to employ a gate constructed so that a liquid seal is formed which precludes the passage of air and gases into the mold cavity and also materially reduces splashing of metal witha 1n the gate during the pouring. Also the gate is preferably formed to communicate with the mold cavity at the bottom and at the top of the cavity and at intermediate points between the top and bottom.

The walls of the mold cavity are suitably coated or treated, in any well-known manner, to reduce as much as possible agitation of the molten metal as it flows into contact therewith, and to insure proper setting of the metal within the mold cavity and a free separation ofthe casting from the mold. The inner Walls of the cavity are also formed so as to provide for venting of the cavity to assure the ready escape of air 01' gases as the molten metal flows 1n.

Suitable means are provided for heating 1 the walls of the mold members I), a, and as the main core d and the core pins e, e are separable from the members I), 0, said parts (Z and 6 may readily be maintained at desired temperatures. As I have fully explained in my application, Serial No. 82,529, the core pins are preferably kept at a temperature substantially lower than the other parts of the mold cavity walls, and the temperature of the gate walls is kept higher thanthe other parts of members 5 and 0,- and'consequentlyawhen the molten metal, at a temperature hundreds of degrees above the temperatures of the mold walls, is poured into the mold cavity it is subjected'to a very strong chilling action at points adjacent the core pins 6, e and to a less marked but very substantial chilling action adjacent other v parts of the cavity walls, while the higher temperature of the gate walls insures the maintenance of molten metal in the gate until afte'r freezing takes place in the mold cavity so that crystallization shrinkage of thecasting proper is obviated by the molten gate metal.

My invention, in its broader aspects, is not limited to the use of any one metal or metallic alloy for the casting; in fact, my copending application, above referred to, mentions several metallic alloys which can be.

used advantageously in the carrying outof the invention. Certain metallic alloys, however, have peculiar advantages and adaptability for the production of castings to meet particular requirements, and the present application relates more especially to a piston casting formed of an aluminum alloy con taining tin and copper/While the proportions of these constituents may be varied somewhat, I prefer an alloy having approximately the following composition: aluminum 94.0 to 94.5%, copper 5.0% and tin 1.0 to 0.5%. I

Inmaking a piston casting of metallic allow such as last referred to, the molten metal, at a suitable temperature between 1350 F. and 1400 F., is poured, by gravity through the gate and into the cavity of the mold. The first "of the molten metal entering the mold cavity fills the bottom thereof (this part of the cavity corresponding to the head of the piston) andthereafter the molten metal, as it enters the mold cavity,'flows from the gate opening in opposite directions around the upright cylindrical parts .of the cavity, the leyel of the metal in the cavity gradually rising'until the cavity is gate. lVhen a brief interval after the pourcasting, with an internal structure such as ing has elapsed, usually as soonas the crystallization shrinkage occurs, the core pins 6, e are Withdrawn; and then after a suitable further interval the core d isremoved,

the mold members 1),. c are separated and the casting removed. I

The chillin elfect of the different parts of the cavity Wa ls upon the metal of the casting, when the casting is of a suitable composition and suitably poured in the manner referred to, gives to the casting physical properties .and internal structural characteristics which are remarkable and, as I believe, greatly superior to any which have heretofore been obtained.

These superior properties and characteristics of my improved'piston castings are: low specific gravity, high coeflicient of heat conductivity, relatively great strength, and a non-porous fine grained structure free from impurities and from cavities due to crystallization shrinkage and with the eutectic substantially surrounding-the excess material in such manner as to provide a durable and efficient bearing surface when the casting is machined. Furthermore the described, has very excellent machining qualities, while, both because of its structural character and the accuracy with which it isformed, little machining is required in producing the finished piston. Again the structure of the metal of the inner walls of the bosses 3, 3, resulting from the relatively quick setting of said metal, is particularly advantageous for-cooperation withthe wristin. p By reason of its fine grained,dense structure the casting,- when machined, takes a high polish and has less tendency to collect carbon than does an iron'piston. I have mentioned the bearing and wearing qualities ofthe casting and, in that connection may add that'I have been unable to note any disintegration in the structure of these castings afterthousands of miles of severe service in relativelv high speed motors of the internal combustion-type; Furthermore, the internal physical structure ofthe casting characteristic of theabove mentioned relation of the eutectic and excess substance is not changed by the working temperatures of theinternal combustion motor to Which caid castings are subjected. y

' WVith respect to the relation of the eutectic and excess substance in my -improved castings,1 I may. observe that while the eutectic substantially'surrounds the excess substance as stated above,I believe it is desirable that internal combustion motor piston casting made of an alloy consisting predominantly of aluminum and containing tin and copper, the casting having chilled walls and being fine grained and substantially free from porosity due to crystallization shrinkage.

2. As anew article of manufacture, an internalcombustion motor pistoncasting made of an alloy consisting predominantly of aluminum and containing other elements such astin and copper in proportions to produ'ce a relatively small quantity of eutectic in the casting after freezing, the casting having the said eutectic substantially surroundin the excess substance therein and having chilled walls.

3. As a new article of manufacture, an internal combustion motor piston "casting made of an alloy consisting predominantly of aluminum and containing other elements such as tin and copper in proportions to produce a elatively small quantity of eutectic in the casting after freezing, the casting having the said eutectic substantially in the casting after-freezing, the casting having. the said eutectic substantially surrounding the excess substance therein and being fine grained and substantially free from porosity due to crystallization shrinkage and entrapped air and other gases.

' In testimony whereof, I hereunto affix my signature.

JOSEPH H. BAMBERG. 

